784 DR FRASER ON THE PHYSIOLOGICAL ACTION 



the vitality of the afferent nerves may be obtained as long as the retained vitality 

 of the spinal cord permits of its diastaltic function being examined. 



4. In mammals and birds, an average dose produces symptoms of asphyxia. 

 When administered to frogs, a similar dose impairs the function of the spinal 

 cord, and diminishes the rates of the cardiac contractions and of the respiratory 

 movements ; and, soon after, the latter cease. In periods varying from one and 

 a-half to four hours afterwards, the motor nerves are paralysed ; this paralysis 

 implicating their endorgans first, and their trunks afterwards. From this it 

 must not be inferred that the nerve is paralysed by a centripetal progression 

 of the poison ; the only fact demonstrated being that a direct ratio exists between, 

 on the one hand, subdivision of nerve substance, facilitating contact of the 

 poison, and, on the other, rapidity of paralysing effect. Indeed, division of the 

 nerve trunk, previous to the administration of Calabar bean, delayed the paralysis 

 of the endorgans. The afferent nerves retain their activity as long, at least, as 

 the functions of the spinal cord are not lost. The spinal cord and the motor 

 nerves are generally paralysed at about the same time. 



5. When a small, but still fatal, dose of Calabar bean is administered to a frog, 

 the effects are the same as those in the previous conclusion, until they arrive at 

 the stage of paralysis of the motor nerves; after this, an interval of several 

 hours may elapse before the functions of the spinal cord are completely sus- 

 pended. During this interval the tactile sensibility of the afferent nerves is 

 increased : so that, if the ischiadic artery and vein of one limb have been tied before 

 the exhibition of the poison, a slight touch of the skin in the poisoned region, 

 which before the administration of the poison caused no effect, will now produce 

 faint twitches of the limb whose vessels are tied ; while an ordinary excitant, 

 such as sulphuric acid, will show everywhere a marked diminution in the 

 diastaltic activity, as measured by the metronome. 



6. With a still smaller dose, a frog may have its cardiac contractions reduced 

 by from seventy to eight per minute, its respiratory movements completely stopped, 

 and the endorgans of its motor nerves paralysed, and yet afterwards completely 

 recover. This has occurred when two grains of extract were administered to a 

 frog, weighing 730 grains. 



7. In frogs, the voluntary muscles are unaffected by the poison, and may 

 continue to respond to galvanic stimulation during three or four days after its 

 administration. The contrast between this and the effect of Calabar bean on 

 the motor nerves, may be well shown by ligaturing the ischiadic vessels of one 

 limb before injecting the poison. If, when strong stimulation causes no reflex 

 movement, the two gastrocnemii muscles with their attached nerves be so 

 placed that an interrupted current, from one Daniell's cell and Dcr Bois 

 Raymond's induction apparatus, may be transmitted simultaneously through 

 either both muscles or both nerve trunks, it will be found in the case of the 



